This invention relates to an optical sensor preferable for a musical instrument and, more particularly, to an optical sensor for producing an electric signal representative of a current position of a moving object and a musical instrument equipped with an array of the optical fiber sensors.
There are several types of a composite keyboard musical instrument. A composite keyboard musical instrument is known as an automatic player piano, and another composite keyboard musical instrument is called as xe2x80x9csilent pianoxe2x80x9d. In the following description, word xe2x80x9clateralxe2x80x9d is indicative of the direction in which black keys and white keys are arranged on the well-known pattern employed in the standard acoustic piano. Word xe2x80x9cperpendicularxe2x80x9d is indicative of the direction crossing the lateral direction at 90 degrees.
The automatic player piano is the combination of an acoustic piano and an electric system for an automatic playing and recording. The electric system includes an array of solenoid-operated key actuators, an array of key sensors and a data processing system. The array of solenoid-operated is usually provided in a space formed in the key bed under the rear portions of the black/white keys, and the array of key sensors is placed on the key bed under the front portions of the black/white keys. A user is assumed to instruct the data processing system to record his performance on the keyboard. While the user is playing a piece of music on the keyboard, the key sensors periodically report the current key positions to the data processing system. The data processing system specifies the times at which the black/white keys are depressed and released, and estimates the loudness of the tones. The data processing system stores these pieces of music data information in music data codes, and records the music data codes representative of the performance in a suitable memory. When the user requests the data processing system to reproduce the tones, the data processing system reads out the music data codes, and determines times to move the black and white keys as well as the values to the key velocity to be imparted to the black and white keys. The data processing system sequentially supplies driving current signals to the solenoid-operated keys at the appropriate timings. Then, the solenoid-operated keys give rise to key motions so as to reproduce the tones.
The silent piano is the combination of an acoustic piano, a hammer stopper and an electronic tone generating system. When a user changes the hammer stopper to a free position, the hammer stopper is moved out of the trajectories of the hammers. While the user is fingering a piece of music on the keyboard, the depressed black/white keys give rise to free rotation of the hammers, and the hammers strike the associated strings so as to generate the piano tones. Thus, the silent piano behaves as an acoustic piano. The user is assumed to change the hammer stopper to a blocking position, the hammer stopper enters the trajectories of the hammers. After the entry into the blocking position, although the depressed key makes the action mechanism escape from the associated hammer, the hammer rebounds on the hammer stopper before striking the string. Any piano tone is not generated from the string. However, the electronic tone generating system produces electronic tones instead of the piano tones. The electronic tone generating system has an array of key sensors, a data processing system and a sound system. While the user is fingering a piece of music on the keyboard, the key sensors periodically report the current key positions of the associated black and white keys to the data processing system. The data processing system specifies the depressed keys and the released keys, and estimates the loudness of the tones. The data processing system stores these pieces of music data information in music data codes, and produces an audio signal from the music data codes. The audio signal is supplied to the sound system, and the sound system such as a headphone converts the audio signal to the electronic tones.
The key sensors may be replaced with hammer sensors. In this instance, the hammer sensors periodically report the current hammer positions to the data processing system, and the data processing system produces the music data codes on the basis of the hammer motion. Thus, the key sensors or the hammer sensors are indispensable components of the composite keyboard musical instrument.
Various kinds of key/hammer sensors have been employed in the composite keyboard musical instrument. Photo-couplers and optical fiber sensors are popular among the manufacturers. The photo-coupler, i.e., a light emitting element and a light detecting are provided on both sides of the trajectory of the associated black/white key, and a light beam is radiated from the light emitting element to the light detecting element across the trajectory of the associated black/white key. A shutter plate is fixed to the lower surface of the associated black/white key, and the shutter plate interrupts the light beam at predetermined points on the trajectory. The light detecting element converts the amount of light incident thereon to photo-current, and the key/hammer position is represented by the potential level converted from the photo-current. The potential level is further converted to a binary value of a digital signal, and the digital signal is supplied to the data processing system as the key/hammer position signal.
The photo-coupler is required for each of the black/white keys or each of the hammers. Eighty-eight keys usually form the keyboard. Accordingly, eighty-eight photo-couplers are to be installed in the narrow space between the key bed and the black/white keys or inside the piano case as close to the strings as possible. Although each photo-coupler is small in volume, the array of eighty-eight keys occupies a substantial amount of space. This results in complicated arrangement inside the piano case.
The optical fiber sensor was proposed in order to make the internal arrangement simple. The optical fiber sensor has a multiple-port sensor head connected through optical fibers to a combined optical element serving as a light emitting element and a light detecting element. Only the multiple-port sensor heads are installed inside the piano case, and the combined optical elements are provided in a relatively wide space. For this reason, the optical fiber sensors are preferable for the combined keyboard musical instrument.
FIG. 1 shows a typical example of the key sensor array implemented by the optical fiber sensors. The prior art key sensor array 50 includes plural sensor heads S1, plural shutter plates 52, pairs of optical fibers 55/60 and combined optical elements (not shown). The sensor heads 51 are formed of transparent acrylic resin, and are arranged at intervals in the lateral direction. The shutter plates 52 are respectively fixed to the lower surfaces of the black and white keys 65 of the keyboard, and are movable together with the associated black and white keys. A light emitting port 53 and a light receiving port 54 are formed in each of the sensor heads 51, and are laterally directed.
As will be better seen in FIG. 2, the sensor heads 51 has a pair of shoulder portions 51a, a bulk portion 51b and a neck portion 51c. The neck portion 51c is narrower than the bulk portion 51b, and the shoulder portions 51a are formed on the steps between the neck portion 51c and the bulk portion 51b. Lenses 57/58 are fixed to the perpendicular surfaces of the shoulder portions 51a, respectively, and slant surfaces 59 are formed in the shoulder portions 51a. The lens 57 and the shoulder portion 51a form the light emitting port 53, and the other lens 58 and the shoulder portion 51a form the light receiving port 54. A pair of holes 61 is further formed in the sensor head 51, and extends from the lateral surface to certain points in the bulk portion 51b. The holes 61 extend in the perpendicular direction, and are directed to the slant surfaces 59. The optical fibers 55 and 60 are inserted into the holes 61, respectively, and are fixed to the bulk portion 51b. Though not shown in FIG. 2, the combined optical elements are connected to the optical fibers 55/60.
Turning back to FIG. 1, the black and white keys 65 are disposed in the narrow spaces each created between the adjacent two sensor heads 51, and, accordingly, the shutter plates 52 have the trajectories in the narrow spaces, respectively. Each of the sensor heads 50 is shared between the adjacent two key sensors 50, and each prior art key sensor is associated with two of the combined optical elements. The optical fiber 55, a half of the bulk portion 51b of a sensor head 51, the light emitting port 53 of the sensor head 51, the light receiving port 54 of the adjacent sensor head 51, a half of the bulk portion 51b of the adjacent sensor head 51 and the two combined optical elements form in combination each prior art key sensor.
When a pianist depresses a black/white key 65, the shutter plate 52 is moved together with the depressed black/white key 65 along the trajectory in the narrow space. The combined optical element emits light, and the light is propagated through the optical fiber 55 to the half of the bulk portion 51b. The light proceeds in the half of the bulk body 51b, and is reflected on the slant surface 59. The light changes the direction, and proceeds to the light emitting port 53. The lens 57 makes parallel light from the reflected light, and the parallel light proceeds to the light receiving port 54 of the adjacent sensor head 51.
The parallel light reaches the light receiving port 54, and the incident light is reflected on the slant surface 59. The light is reflected on the slant surface 59, and is condensed at the end of the optical fiber 60. The light is propagated through the optical fiber 60, and reaches the other combined optical element. The combined optical element converts the light to photo current.
When the shutter plate 52 reaches the optical path between the light emitting port 53 and the light receiving port 54, the shutter plate 65 starts to interrupt the light. While the shutter plate 65 is crossing the optical path, the amount of light incident on the light receiving port 54 is gradually reduced, and, accordingly, the amount of photo current is decreased. Thus, the current position of the black/white key 65 is represented by the amount of photo current.
Only the sensor heads 51 are installed in the narrow space under the black/white keys 65, and make the arrangement in the narrow space simple. However, a problem is encountered in the prior art optical fiber sensor in the assembling work on the optical fibers 55/60 and the sensor head 51. In detail, the optical fibers 55/60 are assembled with the sensor heads 51 as follows. First, the optical fiber 55 is aligned with the hole 61, and inserted into the hole 61 until the leading end is brought into contact with the bottom surface 62. An injector (not shown) is coupled with an injection port 63, and adhesive compound is injected into the injection port 63. The injection port 63 is connected through a passage 64 to the hole 61, and the adhesive compound fills the passage 64. The optical fiber 55 crosses the passage 64 so that the adhesive compound surrounds the leading end portion of the optical fiber 55. When the adhesive compound is solidified, the optical fiber 55 is fixed to the sensor head 51. The other optical fiber 60 is also fixed to the sensor head 51 through the above-described assembling work. Thus, the insertion of the optical fiber 55/60 into the hole 61 and the injection of the adhesive compound are twice repeated for each pair of optical fibers 55/60. The standard keyboard consists of eighty-eight keys. This means that the above-described assembling work is a hundred and seventy-six times repeated for each prior art combined keyboard musical instrument. A large amount of time and labor is consumed, and increases the production cost.
It is therefore an important object of the present invention to provide an optical fiber sensor, component parts of which are easily assembled thereinto.
It is also an important object of the present invention to provide a musical instrument, which is equipped with an array of the optical fiber sensors so as to reduce the production cost thereof.
To accomplish the object, the present invention proposes to pinch an optical guide member between two parts of a sensor head.
In accordance with one aspect of the present invention, there is provided an optical sensor for converting a current position of a moving object to an electric signal comprising a converting unit generating a light and converting an incident light to the electric signal, an optical guide member connected at one end thereof to the converting unit and propagating the light and the incident light between the aforesaid one end and the other end thereof, a sensor head unit connected to the other end of the optical guide member for radiating the light along an optical path and receiving the incident light and having a first portion formed with a guide path which receives a part of the optical guide member and a second portion pinching the part of the optical guide member together with the first portion, and an optical element fixed to the moving object and moved together with the moving object in such a manner as to cross the optical path for varying the amount of an optical property of the incident light depending upon the current position of the moving object.
In accordance with another aspect of the present invention, there is provided a musical instrument for generating tones comprising plural movable members independently moved by a player, a tone generating system associated with the plural movable members for generating the tones specified by the movable members moved by the player and an array of optical sensors for reporting the movable members manipulated by the player to the tone generating system, and each of the optical sensors of the array comprises a converting unit generating a light and converting an incident light to the electric signal, an optical guide member connected at one end thereof to the converting unit and propagating the light and the incident light between the aforesaid one end and the other end thereof, a sensor head unit connected to the other end of the optical guide member for radiating the light along an optical path and receiving the incident light and having a first portion formed with a guide path which receives a part of the optical guide member and a second portion pinching the part of the optical guide member together with the first portion and an optical element fixed to associated one of the plural movable members and moved together with the associated one of the plural movable members in such a manner as to cross the optical path for varying the amount of an optical property of the incident light depending upon the current position of the associated one of the plural movable members.